Blueberry IPM – Cherry Fruitworm (Grapholita packardi), Cranberry Fruitworm (Acrobasis vaccinii)Sonia Schloemann, UMass Extension Fruit Program
Both Cranberry Fruitworm (CBFW) and Cherry Fruitworm (CFW) are native to North America, as are the blueberries they infest. The adult forms of these fruitworms are small brownish-gray or grayish-black moths. Eggs are laid near the calyx of green fruit and are pale creamy color. Larvae found within blueberry fruit in June are small and pale yellowish or pinkish in color. CFW larvae have dark brown heads.
Fruitworms overwinter as larvae in the duff around bushes or field edges and pupate in the spring, emerging as adult moths after the start of bloom and usually before early fruit set. Cherry Fruitworm (CFW) emerges earlier than Cranberry Fruitworm (CBFW). Once mated, moths move into blueberry plantings when fruit is small and green to lay eggs directly on the fruit. Larvae then tunnel into the fruit and begin feeding. Infested fruit turn prematurely blue making them easy to identify when scouting. Larvae will consume from 3-6 berries, filling them with brown frass, and web together fruit with silk. The frass from CFW remains inside the fruit whereas that from CBFW is pushed out and visible. Upon reaching maturity, larvae leave the berries and move to over-wintering sites. There is one generation per year.
Damage: Larvae feed on ripening fruit. Feeding reduces the crop and spoils marketability of the berries.
The important stage to forecast for either species is egg-laying which, for CBFW, occurs during the period of 85-400 GDD Base 50˚F after the onset of sustained adult activity or flight (biofix). Therefore CBFW egg laying is generally predicted to take place during the period of 435-750 GDD Base 50˚F. Modeling for CFW egg-laying is not currently available but is likely somewhat earlier than CBFW.
Eliminate weeds and trash around plants to minimize protective overwintering habitat for larvae.
Clean cultivate between rows to disrupt pupation sites and reduce the population of this pest.
Hand pick and destroy infested fruit in small plantings.
Preserve natural enemies whenever possible by selecting spray materials that are less toxic to beneficials.
Apply recommended insecticides beginning 85 – 100 GDD base 50˚F after sustained trap catches (biofix), which usually coincide with berry-touch or when degree day models reach the action threshold.
If action threshold is reached while some bushes are still in bloom, use materials that are listed as relatively safe for pollinators/parasitoids in chart below that are listed as relatively safe for pollinators/parasitoids.
Avoid use of insecticides with seasonal use restrictions that may be needed for Spotted Wing Drosophila (SWD) control later in the season.
Rotate insecticides from different IRAC groups to reduce the chance of resistance development in the pest.
Use pesticides that are less toxic to predators (e.g., insect growth regulators or B.t. products) to promote populations of natural enemies.
|Trade Names||Chemical Class||Life-stage Activity||Optimal Spray Timing||Pollinator/Parasitoid Toxicity Rating|
|Imidan||Organophosphate||Eggs, larvae, adults||Eggs, larvae, adults||Highly Toxic|
|Lannate/Sevin||Carbamate||Eggs, larvae, adults||Eggs, larvae, adults||Highly Toxic|
|Asana/ Danitol/ Mustang Max/ Hero/ Bifenture||Pyrethroid||Eggs, larvae, adults||Eggs, larvae, adults||Highly Toxic|
|Exirel/ Altacor||Diamide||Eggs, larvae, adults||Eggs, larvae, adults||Relatively Safe|
|Assail||Neonicotinoid||Eggs, larvae, adults||Eggs, larvae, adults||Moderately Toxic|
|Entrust/ Delegate||Spinosyn||Eggs, larvae, adults||Early fruit set over eggs||Moderately Toxic|
|♦Dipel||B.t.||Eggs, larvae, adults||Early fruit set over eggs||Relatively Safe|
|Intrepid/ Confirm||Growth Regulator||Eggs, larvae, adults||Early fruit set over eggs||Relatively Safe|
|♦Grandevo/ ♦Venerate||Biologicals||Eggs, larvae, adults||Early fruit set over eggs||Relatively Safe|
|Rimon||Growth Regulator||Eggs, larvae, adults||Early fruit set under eggs||Relatively Safe|
|Esteem||Growth Regulator||Eggs, larvae, adults||Early fruit set under eggs||Relatively Safe|
♦OMRI certified for organic production.
 Michigan State Univ. Fruit Crop Advisory, Fruitworm Control in Blueberries (R. Isaacs, J. Wise) 5/17/16.
This work was supported by the Crop Protection and Pest Management Extension Implementation Program, Grant No. 2014-70006-22579 from the USDA-National Institute of Food and Agriculture.